Radio controlled timepieces receiving standard radio waves including time information with small antennas to automatically correct the time are actively commercialized as technologies are developed for smaller high-performance antennas, receiving apparatuses with low power consumption, cost reduction, etc. Transmitting stations transmitting standard radio waves are constructed not only in Japan but also other countries and regions such as America, Europe, and Asia, and spreading across the world. Therefore, it has become possible to receive standard radio waves from a plurality of transmitting stations in more and more countries and regions, and as internationalization has advanced, such a chance has been increasing that users of radio controlled timepieces travel all over the world and receive standard radio waves of each country or region.
However, the standard radio waves have a different time information format for each country, and transmission frequencies may be different in countries or regions. Therefore, to receive the standard radio waves of each country and region to obtain the time information, a radio controlled timepiece needs unit for switching decoding algorithms that decode the time information formats correspondingly to the standard radio waves of each transmitting station and unit for switching reception frequencies if transmission frequencies are different. A manual reception switching mode and an automatic reception switching mode are proposed for the switching unit for receiving the standard radio waves from a plurality of transmitting stations.
In the manual reception switching mode, a user of the radio controlled timepiece recognizes a transmitting station available in the country or the region where the user is positioned, and switches a transmitting station for reception with a reception changeover switch, etc. to receive the standard radio waves. In this case, it is inconvenient since the user must recognize the transmitting station that transmits the standard radio waves in each country and region and operate the reception changeover switch, etc. for switching the reception. Furthermore, it is very problematic that an accurate time cannot always be displayed since a transmitting station suitable for reception of the standard radio wave may not be selected.
To solve such problems, for one of the automatic reception switching modes, a time data reception apparatus is proposed that switches a reception frequency of standard radio waves in accordance with frequencies stored in a storing unit that which determines whether the reception of the standard radio wave succeeds or fails and that selects the standard radio wave suitable for reception among standard radio waves with different frequencies (for example, see patent document 1).
According to this proposed technique, the time data reception apparatus includes a receiving unit that receives a plurality of standard radio waves with different frequencies, a reception frequency switching unit that switches a frequency of the received standard radio wave, a controlling unit that controls the reception frequency switching unit, and a current time correcting unit that corrects current time data based on received time data. The time data reception apparatus further includes a success/failure determining unit that determines whether the receiving unit has succeeded or failed in reception of the standard radio wave, and a storing unit that stores reception frequencies. The controlling unit controls the reception frequency switching unit such that a frequency of the standard radio wave received by the receiving unit is switched to the frequency stored in the storing unit. If the success/failure determining unit determines that the reception has been failed, the reception frequency switching unit is controlled to switch a frequency, and if the success/failure determining unit determines that the reception has been succeeded, the frequency of the standard radio wave received by the receiving unit can be stored in the storing unit. As a result, a successfully received standard radio wave can be quickly selected from a plurality of standard waves with different frequencies and time information can be obtained from the selected standard radio wave to correct the time automatically.
In another automatic reception switching mode, the standard radio waves with different frequencies are sequentially received by a receiving unit that receives the standard radio waves, and a reception state is detected for each standard radio wave by a reception state detecting unit. The standard radio wave for obtaining time information is designated based on the difference of the reception states (for example, patent document 2).
This proposed technique includes a receiving unit that sequentially receives the standard radio waves with different frequencies, a reception status detecting unit that detects the reception states of the standard radio waves received by the receiving unit, a received signal designating unit that designates one standard radio wave for obtaining time information from among the standard radio waves based on each reception state detected by the reception status detecting unit, and a time information obtaining unit that obtains time information from the standard radio wave designated by the received signal designating unit. The automatic time correction can be performed with the obtained time information. As a result, since each of the standard radio waves with different frequencies is received to be detected the reception state thereof, the time information can be obtained by designating the standard radio wave suitable for reception, and a reliable radio controlled timepiece can be realized.
Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2003-270370 (claims, FIG. 1)
Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2002-296374 (claims, FIG. 1)